Conveyors are used to discharge material at a fixed height above ground to stack material such as agglomerated material, ore, or minerals. Such conveyors are typically included in stackers or other devices used to discharge material at a fixed height. U.S. Pat. Nos. 3,185,290, 4,029,200, 4,245,732, 4,406,361, 4,629,060, 4,907,932, 5,181,600, 6,360,876, and 6,896,123 disclose different types of conveyor apparatuses or stackers.
Some conveyed materials such as agglomerated ore are sensitive to drop height. Often, luffing conveyors are used to reduce the drop height of the material. Reducing the drop height can help reduce degradation or spoilage of the material being stacked. Many types of luffing conveyors are configured to move the whole conveyor, which complicates its receiving hopper and can substantially increase the cost of such machines.
In alternative luffing conveyor designs, a luffing conveyor includes a luffing end that can be affixed to a fixed conveyor to lower the drop height of a stacker or other stacking device or conveyor apparatus. Typically, a hinged luffing conveyor has a bend pulley affixed at the hinge point of the conveyor. The conveyor belt must transition from a troughed area to a flat portion and back to a troughed area in a relatively short distance. At some luffing discharge angles, the material can lift off of the belt as it transitions over the hinge pulley such that the material falls back on the belt at a higher velocity than the belt speed, losing traction between the material and the belt. As a result, material may fall from an undesirably high height, which increases degradation and spillage. This is particularly true for large luffing discharge angles.
A conveyor apparatus is needed to more consistently convey material to a desired drop height, particularly at large luffing discharge angles. Preferably, such a conveyor apparatus eliminates the need for a fixed bend pulley and can increase the belt life of the conveyor.